1. Field of The Invention
The present invention relates to a process and apparatus for extruding dough, particularly for yeast dough, crisp breads and puffed breakfast cereals.
The present invention also relates to an extruder die head and more particularly, to dough guides fastened to the die head.
2. Description of The Prior Art
Extruders currently used for processing yeast dough, crisp breads and puffed breakfast cereals are known and generally comprise one or more feed hoppers which regulate the dry ingredients fed into a twin screw cooker/extruder where water is directly added to the dry ingredients by means of a metering pump.
U.S. Pat. No. 4,217,083 discloses a complete baking-extrusion-expansion process as shown in FIG. 1, with the extrusion head being the novelty of the invention. The extrusion head has a horizontal slot from which dough is extruded onto two pivotable extension bars. Also, note straps 22 of FIG. 6.
The article entitled "Extruded Crisp Bread Fast Mover In Europe", published in the magazine Snack Food Oct. 19, 1982, discusses a twin screw cooker-extruder in which dough is extruded horizontally and passed onto a gauge roll which feeds to the cutter.
Because texture and shape are highly important in the manufacturing of food, and particularly for dough products, it is particularly important to maintain rigid controls upon the final end product. The prior art apparatus and process fail to provide a final dough product that is uniform in thickness (shape). Sporadic surging of dough from the die head and extreme expansion of dough are not corrected by prior art processes and apparatus. Thus, from time to time, a product like crisp breads, for example, is non-uniform in thickness and in degree of expansion.
Moreover, because the prior art extrudes the dough from a horizontal die slot, and then immediately deposits the dough on a conveyor belt, the texture of the dough is non-uniform. The upper surface of the dough is generally more cellular and lighter in color than the bottom surface which contacts the conveyor belt. Also, the texture is non-uniform because occluded gases within the dough are much hotter than ambient gases and thus tend to rise. The upper horizontal surface of the extruded dough easily allows the gases to evaporate from the dough, thus forming a textured cellular surface. However, the lower horizontal surface of the extruded dough often times does not have the same texture as the upper horizontal surface. This is due to the fact that the occluded gases near the lower horizontal surface of the extruded dough attempts to escape from the dough by rising from the lower horizontal side of the dough to the upper horizontal surface. Some occluded gases do, of course, escape by evaporating from the lower horizontal surface of the extruded dough.
When the occluded gas evaporates from the extruded dough, the cellular texture product results. The cellular texture disperses the light impinging on the final product causing a lighter color as compared to a surface which is non-cellular or in which the cellular formation is not uniform. Therefore, the prior art baked dough does not have a consistent uniform color from side to side.
Neither the article nor U.S. Pat. No. 4,217,083 disclose an extruder with an attached dough guide for preventing the expanding dough issuing from the extruder from being too irregular, nor do they disclose a vertically oriented die to produce a more uniformly textured product.
Often it is particularly desirable to vary the width of the dough guide to provide different degrees of guidance of the extruded dough and thus produce products of varying sizes by merely employing different sized dies and adjusting the dough guide to accommodate the die.